The use of video tape cassettes in video recorders is now widespread. In certain video recorders, particularly those known as "U-Matic" recorders, it has been found that edge damage to the tape occurs if the supply reel spindle and/or the take-up reel spindle of the recorder is improperly adjusted or misaligned. In such systems, the tape packs are contained in the tape cassette in such manner as to allow the tape to undergo vertical small displacements within the cassette. However, when the cassette is inserted into the video recorder, the tape packs are supported in a fixed position within the cassette by the supply reel spindle and the take-up reel spindle. In an optimally aligned system, the height of each spindle is adjusted to support the tape packs in such manner that the moving tape will not come into contact with either the top or bottom of the cassette, or make improper contact with certain other elements of the tape recorder. However, if the height of either or both spindles deviates even slightly from the nominal height, the tape edges may come into contact with the cassette housing or make improper contact with the recorder, and be susceptible to serious damage.
Because of the above-described problem, precise adjustment of the spindle heights in video tape recorders is of great importance. An early solution suggested in the prior art is known as a "go/no-go" gauge which is essentially a precisely machined piece of small metal which can be aligned with the spindle to determine if the spindle height is correctly adjusted. However, the use of the go/no-go gauge requires disassembly of a section of the recorder, which is a cumbersome and time-consuming procedure.
An alternative prior art solution is a device known as the "Memorex Spindle Height Alignment Gauge", manufactured by the Memorex Corporation, Santa Clara, California. This device consists of a pair of gauges positioned in a plastic (Delrin.RTM.) base which is of the general size of a video cassette, including two cylindrical openings which accomodate the recorder spindles when the device is inserted into position in a video recorder in lieu of a cassette. The spindles come into contact with a movable element which is interconnected with the gauges by an elaborate system of levers to provide an indication of the spindle height. The stability and reproducibility of measurements using this prior art device have proved to be a problem, particularly when the instrument is subject to repeated handling. In a more recent version, a complicated overriding clutch mechanism has been included as a partial solution to the stability problem.
An additional problem of this device is that the calibration of the gauge between uses involves a "set-up block" onto which the gauge is placed for calibration. The set-up block, itself, is a facsimile of the spindle arrangement in a video recorder, and appears to be relatively complicated and expensive to manufacture.